This invention relates to a recorded information reproducing apparatus that can make a high-speed response at the reproduction start and the jump operation in reproduction of continuous information of a moving picture, voice, etc., and can reproduce information in mixed modes of standard-speed reproduction and special reproduction at double speed, quad speed, etc., (forward, backward).
Hitherto, a video server has been available as a system for recording and reproducing continuous information of a moving picture, voice, etc. The video server generally consists of a disk array, a memory buffer, read request acceptance means, and data read means. The disk array is used as RAID (redundant array of independent disks) for striping data and storing the data. When data is read, an area containing desired data is read from disk and is stored in the FIFO memory buffer. A response to a data read request is completed by separating the desired data from the buffer and sending the data to the read requester.
To guarantee the data read speed, the video server processes read of continuous information data requested by a terminal from disk in order within a given period called a time slot. Since read of the data requested by the terminal and assigned to the time slot is always processed while one cycle of the time slot is completed, the read speed from the disk is guaranteed. If a new read request is made on the terminal, for example, for reproduction start or jump, it is newly assigned to time slot.
If new assignment to time slot is possible in the time slot at the request acceptance time, when the read request is accepted while processing stored in the first portion in the time slop is performed and processing of the read request is assigned to the end of the time slot, the read request wait time reaches the maximum and becomes the time as much as one cycle of the time slot.
Since each request for reading data from disk is once processed in one period of a time slot, a sufficient amount of data that can respond to read request from a terminal during the one period must be read into the memory buffer at a time.
However, in the above-described related art, when reproduction of a moving picture is started, data is supplied to the memory buffer before the moving picture can be reproduced. This means that the time taken for filling the memory buffer with data becomes the response time. This also applies to reproduction position change made because of jump during reproduction. To change the reproduction position, it is necessary to discard the data in the buffer, newly read data at the jump destination position and later, and fill the buffer with the read data. Thus, a high-speed response cannot be provided at the moving picture reproduction start time or the jump operation.
For example, in the video server in the related art, the response time at the moving picture reproduction start time is as follows: Assuming that the number of terminals is 40, that the number of disks is 5, that the data read unit is 256 Kbytes, and that the average read speed of one disk when data is read in (256/5)-Kbyte units is 1.5 Mbytes/sec, the required time for one cycle of a time slot, T, is
T=256xc3x9740/(1.5xc3x971000xc3x975)
about 1.4 seconds. That is, the response to the reproduction start takes 1.4 seconds.
The video server in the related art is predicated on sequential read of data of continuous information of a moving picture, voice, etc. This can also be understood from the fact that data is preread sequentially into the memory buffer described above. Then, if data of continuous information is specially reproduced at double speed, quad speed, etc., the data read speed from disk also becomes double or quad, and the buffer memory needs to have twice or four times the normal capacity. This means that when special reproduction at double speed or quad speed is executed from standard-speed reproduction, a high-speed response cannot be provided either.
Thus, whenever the reproduction state is changed at the standard reproduction start time, the special reproduction start time, the jump time, etc., a high-speed response cannot be provided.
It is therefore an object of the invention to provide a recorded information reproducing apparatus that can make a high-speed response at the reproduction start time and the jump time in reproduction of continuous information of a moving picture, voice, etc., and can make a high-speed response if change is made from standard-speed reproduction to special reproduction at double speed, quad speed, etc., (forward, backward), and can reproduce information in mixed modes of standard-speed reproduction and special reproduction.
To the end, according to a first aspect of the invention, there is provided a continuous recorded information reproducing apparatus for adopting a data record technique of storing continuous information data of moving picture information, voice information, etc., on a plurality of disks in order from the top in arbitrary data size units and reading and reproducing the recorded continuous information data, the continuous recorded information reproducing apparatus comprising disk management means for managing the load state on each disk, namely, the data read state, read means for reading data from a specified position of a disk, read prediction control means for accepting a read request containing data read position information together with reproduction state information indicating reproducing or reproduction start, looking up the load state on each disk in the disk management means, determining whether or not the requested data can be read within a stipulated time based on the load state on the disk storing the data and prediction of a data read state at the next time, and instructing the read means to read the data from the specified position of the disk, reproduction start time alternative rule storage means for storing an alternative rule for reading alternative data at reproduction start time, and read position conversion means for converting the data read from the specified position of the specified disk into a disk from which data can be read within the stipulated time and a read position on the disk according to the rule stored in the reproduction start time alternative rule storage means based on the reproduction state information indicating the reproduction start.
Thus, the continuous recorded information reproducing apparatus can be provided that can guarantee the response speed at the reproduction start time within the stipulated time by reading data from the disk from which data can be read within the stipulated time at the reproduction start time of new continuous data although read of any other data being reproduced is not hindered.
According to a second aspect of the invention, there is provided a continuous recorded information reproducing apparatus comprising jump time alternative rule storage means for storing an alternative rule at the jump time for changing the reproduction position.
Thus, the continuous recorded information reproducing apparatus can be provided that can guarantee the response speed at the jump time within the stipulated time because of reading data from the disk from which data can be read within the stipulated time at the jump time in reproduction of continuous data although read of any other data being reproduced is not hindered.
According to a third aspect of the invention, there is provided a continuous recorded information reproducing apparatus comprising special reproduction time alternative rule storage means for storing an alternative rule at the time of special reproduction such as double-speed reproduction or quad-speed reproduction.
Thus, the continuous recorded information reproducing apparatus can be provided that can execute special reproduction data read and make a high-speed response that the required time when the reproduction state is changed from the standard reproduction state to special reproduction is also within the stipulated time although read of any other data being reproduced is not hindered.
According to a fourth aspect of the invention, there is provided a continuous recorded information reproducing apparatus comprising read request acceptance and issuance means for accepting a read request, assigning a priority to the read request, and periodically issuing the read request.
Thus, the continuous recorded information reproducing apparatus can be provided that can make a high-speed response to the reproduction start time of new continuous data, jump in reproduction of continuous data, or reproduction state change from standard reproduction to special reproduction within the stipulated time in mixed modes of standard reproduction and special reproduction although read of any other data being reproduced is not hindered.
The first to fourth aspects of the invention can be modified as follows:
any combination thereof;
a data record technique in which if the continuous information data is moving picture information, the information data pieces are stored under the same rule (for example, on a plurality of disks in order from the top) in data size units of one-frame data of the moving picture;
a data record technique in which if the continuous information data is moving picture information in an MPEG format, the information data pieces are stored under the same rule (for example, on a plurality of disks in order from the top) in 1-GOP data units;
the stipulated time for determining whether or not data can be read is the one-frame time in a moving picture, for example, 33 msec at a rate of 30 frames per msec;
the reproduction start time alternative rule is to forward shift one frame at a time, namely, k+n (n=1, 2, 3 . . . ) with respect to read request frame number k;
the jump time alternative rule is to forward shift one frame at a time, namely, k+n (n=1, 2, 3 . . . ) with respect to read request frame number k;
the jump time alternative rule is to backward shift one frame at a time, namely, kxe2x88x92n (n=1, 2, 3 . . . ) with respect to read request frame number k;
the special reproduction time alternative rule is to forward shift one frame at a time, namely, k+n (n=1, 2, 3 . . . ) with respect to read request frame number k;
the special reproduction time alternative rule is to backward shift one frame at a time, namely, kxe2x88x92n (n=1, 2, 3 . . . ) with respect to read request frame number k;
if the special reproduction time alternative rule is to shift a maximum of nxe2x88x921 frames at a time at n-times-speed reproduction time and an alternative frame is retrieved, when it is determined that data cannot be read within one-frame time, the frame data read at the preceding time is used, etc.